1. Field of the Invention
The present invention relates to lightweight modular structures in general and more particularly to an adjustable frame for supporting a lightweight modular building.
2. Discussion of Background
Modular frame structures comprised of interfitting members are commonly used for making lightweight, non-permanent or semi-permanent buildings, including greenhouses, tents, screened-in patios, and storage buildings.
For example, U.S. Pat. No. 5,255,698 describes a tent frame having a pair of opposing A-frame ends and center T-support member. The frame can be collapsed for transportation or storage and then quickly set up when needed.
U.S. Pat. No. 3,165,110 describes a lightweight modular building frame which is supported by a plurality of resilient arcuate members. The resilient support members are held together with rigid connecting members. U.S. Pat. No. 3,051,185 discloses an arched shelter structure similar to that of U.S. Pat. No. 3,165,110, except that in U.S. Pat. No. 3,051,185 the arched members are rigidly arched and not resiliently bent into an arched configuration.
It is known to provide a building of a plurality of lightweight interfitting parts so that the frame can be easily assembled, disassembled and transported. It is also common, as in the flames described in U.S. Pat. Nos. 5,255,698 and 3,480,023, to provide a foldable building frame which can be maintained in an assembled configuration, but folded for convenience in transportation or storage.
None of the above frames, however, can be easily adjusted in size so that a single frame can be adjusted to meet different purposes. This is unfortunate, because for greenhouses in particular, it would be advantageous to adjust the height of the frame supporting the greenhouse so that the greenhouse can be configured to accommodate the different growth rates of different vegetation. This will not only reduce the amount of covering material required for the greenhouse during certain months, but will also reduce the air volume within the greenhouse. By reducing the air volume within the greenhouse, the total amount of air that is required to be heated in the colder months by an external heating source is also reduced.
The utility of any modular lightweight building frame would be enhanced if the height, length and width could be independently and simultaneously adjusted. In a storage building, for example, a size adjustment feature greatly facilitates efficient use of space.
There remains a need for a lightweight modular frame comprising a plurality of interfitting parts that enables the frame to be easily enlarged or reduced in size, and adjusted in place without adding or subtracting components from the structure.